Molecular Biomarkers For Environment Carcinogens. A major goal of public health practice is disease prevention. The development of molecular biomarkers for exposures to environmental carcinogens will greatly facilitate the identification of individuals at high risk for disease outcomes. In addition, we view the development of intermediate biomarkers as essential to the timely development of the field of chemoprevention. Thus, it is the goal of this program project to bring together an interdisciplinary group of researchers whose interests are to develop biomarkers applicable to the different times during the multi- stage progression of cancer from initiation to tumor diagnosis. The scientific aspects of this Program Project grant consists of three projects and two core laboratories. Project I: Molecular Biomarkers for Human Liver cancer is led by Dr. Groopman. This project will develop and validate molecular biomarkers for aflatoxins in carriers and non-carriers of Hepatitis B virus who reside in The Gambia, West Africa and Qidong County, P.R.C. Project II: Molecular Dosimetry of Ingested Polycyclic Aromatic Hydrocarbons and Heterocyclic Amines is led by Dr. Strickland. This project seeks to develop and validate biomarkers specific for dietary exposures that have been associated with increased risk for cancers of the gastrointestinal tract. Project III: Modulation of Biomarkers of Aflatoxin-Exposure by Oltipraz is led by Dr. Kensler. This project will apply intermediate biomarkers to the field of chemoprevention with the eventual goal of human intervention studies. Finally, there are proposed two core laboratories. Core A: Cytochrome P-450 and Acetylator Metabolic Phenotyping Using Urinary Markers in human samples. Core B: Biostatistics/Epidemiology led by Dr. Munoz. These cores will be general resources for all investigators in the Program Project.